The present invention generally relates to spindle motor control methods and disk units, and more particularly to a spindle motor control method for positively stopping rotation of a spindle motor and to a disk unit which employs such a spindle motor control method.
In disk units such as magnetic disk units, optical disk units and magneto-optic disk units, a spindle motor rotates a recording medium such as a magnetic disk, optical disk and magneto-optic disk. The spindle motor rotates the disk during operation of the disk unit, but in a power save mode or the like, the spindle motor is stopped in order to reduce the power consumption. In addition, when the disk is loaded into the disk unit, the disk is mounted on a spindle which is rotated by the spindle motor. On the other hand, when unloading the disk from the disk unit, the disk is removed from the spindle. There is a possibility of a recording surface of the disk from becoming damaged if the spindle rotates while loading and unloading the disk to and from the disk unit, and for this reason, the spindle motor is stopped when loading and unloading the disk to and from the disk unit.
When stopping the spindle motor, there is a demand to positively stop the rotation of the spindle motor within a short time from a start of a stop operation. If the rotation of the spindle motor actually does not stop completely even when the stop operation is carried out, there is a possibility of damaging the disk when loading and unloading the disk to and from the disk unit. Furthermore, if it takes time for the actual rotation of the spindle motor to completely stop after the start of the stop operation, it takes that much time to load and unload the disk to and from the disk unit in a case where the loading and unloading of the disk is prohibited until the rotation of the spindle motor comes to a complete stop, and the operation characteristic of the disk unit becomes poor.
Conventionally, there is a spindle motor which is provided with a Hall element for detecting the rotation of the spindle motor. According to this spindle motor, a brake signal is supplied to the spindle motor based on a rotation detection signal which is detected by use of the Hall element, so as to stop the rotation of the spindle motor. It is possible to judge whether or not the spindle motor is stopped based on the rotation detection signal.
But recently, in order to reduce the cost of the spindle motor, there are disk units which use a type of spindle motor which is not provided with a Hall element. For this reason, it is impossible to judge whether or not this type of spindle motor is stopped based on the rotation detection signal described above.
Hence, in the case of this type of spindle motor which is not provided with a Hall element, there is no means of detecting whether or not the spindle motor is stopped, and a brake signal is turned ON/OFF by use of a timer or the like when stopping the spindle motor.
However, when the brake signal is supplied to the spindle motor when stopping the spindle motor which is undergoing a steady state rotation, there was a problem in that it is impossible to positively and accurately stop the spindle motor by simply turning the brake signal ON/OFF by determining a brake time by use of the timer or the like, because a deceleration value at an initial stage of the brake time slightly differs for each individual spindle motor. In addition, since the characteristic of the spindle motor is temperature dependent, there was also a problem in that an accurate brake time cannot be obtained when a temperature change occurs. In these cases, because an appropriate brake time cannot be obtained, the spindle motor continues to rotate in a forward direction due to inertia if the brake time is too short, and the spindle motor starts to rotate in a reverse direction due to inertia if the brake time is too long.
Conventionally, the possibility of the spindle motor slightly rotating due to inertia is taken into consideration, and after the supply of the brake signal to the spindle motor is stopped, the spindle motor is regarded stopped after a predetermined time elapses from the stop of the brake signal supply by use of a timer. As a result, there was a problem in that it takes time to detect the stop of the spindle motor, and when this spindle motor is applied to the disk unit, there was a problem in that the operation characteristic of the disk unit becomes poor when loading and unloading the disk to and from the disk unit.